Dual role antenna assembly

Abstract

A dual role antenna assembly operable for use with GEO and LEO / MEO satellites has at least two curled inverted-F substantially omnidirectional antennas mounted on a ground plane. The antennas have asymmetrical gain patterns favoring certain sectors and are oriented such that the favored sectors of the different antenna face different directions. A controller selects the antenna for connection to an RF front-end in accordance with predetermined performance criteria.

Description

FIELD OF THE INVENTION[0001]This invention relates to the field of antenna, and more particularly to a dual role antenna assembly operable for use with use with geostationary earth orbit (GEO) and low earth orbit / medium earth orbit (LEO / MEO) satellite constellations, and to a method of controlling such an antenna.BACKGROUND OF THE INVENTION[0002]Designers of mobile satellite communication antenna systems are faced with a number of conflicting system requirements. The link budget benefits from higher gain, but an omnidirectional pattern is best from a system coverage perspective. The antennas should be low profile and yet have good low elevation angle performance. They should also be small and yet have sufficiently wide bandwidth.[0003]Exploring these trade-offs typically leads to the selection of patch antenna technology if maintaining a low profile is critical, or helical antennas if profile is less important but low elevation angle performance is vital. Furthermore, maintaining lo...

AI Technical Summary

Benefits of technology

[0009]Embodiments of the invention employ a diversity antenna system that uses a tilted radiation pattern to enhance low elevation angle gain for one higher priority satellite, while maintaining sufficient omnidirectionality to function well with the remaining satellites.

[0011]It will be understood that substantially omnidirectional in this context means that the antenna generally has all round coverage to receive (or transmit) signals from any direction outside of a small exclusion zone where reception (or transmission) is impaired. However, a radiation pattern is never completely uniform and in practice one direction has higher gain. Also, the gain pattern is generally tilted relative to the horizon, so that one sector will have better low elevation performance.

[0015]The bandwidth limitations of the CIFA element can be partly overcome by increasing the height the antenna, for example, by doubling the height to 12 mm. Thus, the height of the curled inverted-F antenna should be at least 12 mm for good bandwidth performance in GEO systems with typical manufacturing tolerances. However, in addition, multiple feed strips can be provided for the antenna to optimize its performance for multiple sub-bands. An RF switching module is provided in this case to switch between the feed strips according to the required sub-band depending on the particular frequency in use.

[0017]Unlike MBAs in the prior art, where the object is usually to create a directional beam, in accordance with the present invention the object of the MBA is to achieve omnidirectional coverage. The composite radiation pattern is achieved by connecting the RF front-end directly to the array element corresponding with the desired beam pattern. The superposition of individual element radiation patterns creates and an aggregate MBA radiation pattern. Keeping only one element active at a time is necessary to ensure that the MBA effective aperture area remains small, facilitating a more omnidirectional radiation pattern.

[0019]To facilitate the design of the underlying antenna element, it is preferable to have the systems involved operate in nearby frequency bands. This enables simultaneous GEO / GNSS operation with the same RF front-end.

Problems solved by technology

However, a radiation pattern is never completely uniform and in practice one direction has higher gain.

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